Biological parameters of franciscana
dolphins, Pontoporia
blainvillei, by-caught in artisanal fisheries off southern Buenos Aires,
Argentina
María Fernanda Negri, María Victoria Panebianco, Pablo
Denuncio, María Natalia Paso Viola, Diego Rodríguez and Humberto Luis
Cappozzo
Abstract
The franciscana dolphin (Pontoporia
blainvillei) is a small coastal dolphin endemic to the south-western
Atlantic Ocean. Incidental captures in fishing gillnets is possibly the greatest
conservation concern for this species, and occurs within most of its
geographical distribution. The aim of this paper is to determine the biological
parameters of franciscana dolphin by-caught from artisanal coastal fisheries of
the southern Buenos Aires province, Argentina. Between 2003 and 2009, carcasses
of 54 incidentally captured franciscanas were collected. The age, sexual and
physical maturity and body condition of each specimen was determined. The
sex-ratio of the by-caught dolphins did not differ from parity and, consistent
with other areas, juveniles younger than 4 yr old were captured in higher
proportion (69%). In addition, 74% of the entangled animals were sexually
immature and 85% physically immature. Sexually immature dolphins were
predominant in the spring, a period which coincides with the breeding season. An
assessment of the body condition of captured franciscanas suggests that
entanglements were not associated with a disease or physiological disorder. The
results presented here are important to assess the impact of artisanal fisheries
on the population of franciscana dolphins in the southernmost area of its
distribution.
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